diff options
Diffstat (limited to 'lib/util/dlinklist.h')
| -rw-r--r-- | lib/util/dlinklist.h | 170 |
1 files changed, 111 insertions, 59 deletions
diff --git a/lib/util/dlinklist.h b/lib/util/dlinklist.h index c1f01e616a..6d525f9036 100644 --- a/lib/util/dlinklist.h +++ b/lib/util/dlinklist.h @@ -1,7 +1,8 @@ /* Unix SMB/CIFS implementation. some simple double linked list macros - Copyright (C) Andrew Tridgell 1998 + + Copyright (C) Andrew Tridgell 1998-2010 This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -23,71 +24,94 @@ #ifndef _DLINKLIST_H #define _DLINKLIST_H +/* + February 2010 - changed list format to have a prev pointer from the + list head. This makes DLIST_ADD_END() O(1) even though we only have + one list pointer. + + The scheme is as follows: + + 1) with no entries in the list: + list_head == NULL + + 2) with 1 entry in the list: + list_head->next == NULL + list_head->prev == list_head + + 3) with 2 entries in the list: + list_head->next == element2 + list_head->prev == element2 + element2->prev == list_head + element2->next == NULL + + 4) with N entries in the list: + list_head->next == element2 + list_head->prev == elementN + elementN->prev == element{N-1} + elementN->next == NULL -/* hook into the front of the list */ + This allows us to find the tail of the list by using + list_head->prev, which means we can add to the end of the list in + O(1) time + + + Note that the 'type' arguments below are no longer needed, but + are kept for now to prevent an incompatible argument change + */ + + +/* + add an element at the front of a list +*/ #define DLIST_ADD(list, p) \ do { \ if (!(list)) { \ - (list) = (p); \ - (p)->next = (p)->prev = NULL; \ + (p)->prev = (list) = (p); \ + (p)->next = NULL; \ } else { \ + (p)->prev = (list)->prev; \ (list)->prev = (p); \ (p)->next = (list); \ - (p)->prev = NULL; \ (list) = (p); \ - }\ + } \ } while (0) -/* remove an element from a list - element doesn't have to be in list. */ +/* + remove an element from a list + Note that the element doesn't have to be in the list. If it + isn't then this is a no-op +*/ #define DLIST_REMOVE(list, p) \ do { \ if ((p) == (list)) { \ + if ((p)->next) (p)->next->prev = (p)->prev; \ (list) = (p)->next; \ - if (list) (list)->prev = NULL; \ + } else if ((list) && (p) == (list)->prev) { \ + (p)->prev->next = NULL; \ + (list)->prev = (p)->prev; \ } else { \ if ((p)->prev) (p)->prev->next = (p)->next; \ if ((p)->next) (p)->next->prev = (p)->prev; \ } \ - if ((p) != (list)) (p)->next = (p)->prev = NULL; \ + if ((p) != (list)) (p)->next = (p)->prev = NULL; \ } while (0) +/* + find the head of the list given any element in it. + Note that this costs O(N), so you should avoid this macro + if at all possible! +*/ #define DLIST_HEAD(p, result_head) \ do { \ - (result_head) = (p); \ - while (DLIST_PREV(result_head)) (result_head) = (result_head)->prev; \ + (result_head) = (p); \ + while (DLIST_PREV(result_head)) (result_head) = (result_head)->prev; \ } while(0) /* return the last element in the list */ -#define DLIST_TAIL(list, result_tail) \ -do { \ - (result_tail) = (list); \ - while ((result_tail) && (result_tail)->next) (result_tail) = (result_tail)->next; \ -} while (0); +#define DLIST_TAIL(list) ((list)?(list)->prev:NULL) /* return the previous element in the list. */ -#define DLIST_PREV(p) ((p)?(p)->prev:NULL) - -/* promote an element to the top of the list */ -#define DLIST_PROMOTE(list, p) \ -do { \ - DLIST_REMOVE(list, p); \ - DLIST_ADD(list, p); \ -} while (0) - -/* hook into the end of the list - needs the entry type */ -#define DLIST_ADD_END(list, p, type) \ -do { \ - if (!(list)) { \ - (list) = (p); \ - (p)->next = (p)->prev = NULL; \ - } else { \ - type tmp; \ - for (tmp = (list); tmp->next; tmp = tmp->next) ; \ - tmp->next = (p); \ - (p)->next = NULL; \ - (p)->prev = tmp; \ - } \ -} while (0) +#define DLIST_PREV(p) (((p)->prev && (p)->prev->next != NULL)?(p)->prev:NULL) /* insert 'p' after the given element 'el' in a list. If el is NULL then this is the same as a DLIST_ADD() */ @@ -96,34 +120,62 @@ do { \ if (!(list) || !(el)) { \ DLIST_ADD(list, p); \ } else { \ - p->prev = el; \ - p->next = el->next; \ - el->next = p; \ - if (p->next) p->next->prev = p; \ + (p)->prev = (el); \ + (p)->next = (el)->next; \ + (el)->next = (p); \ + if ((p)->next) (p)->next->prev = (p); \ + if ((list)->prev == (el)) (list)->prev = (p); \ }\ } while (0) -/* demote an element to the end of the list, needs the entry type */ -#define DLIST_DEMOTE(list, p, type) \ + +/* + add to the end of a list. + Note that 'type' is ignored +*/ +#define DLIST_ADD_END(list, p, type) \ do { \ - DLIST_REMOVE(list, p); \ - DLIST_ADD_END(list, p, type); \ + if (!(list)) { \ + DLIST_ADD(list, p); \ + } else { \ + DLIST_ADD_AFTER(list, p, (list)->prev); \ + } \ } while (0) -/* concatenate two lists - putting all elements of the 2nd list at the - end of the first list */ -#define DLIST_CONCATENATE(list1, list2, type) \ +/* promote an element to the from of a list */ +#define DLIST_PROMOTE(list, p) \ do { \ - if (!(list1)) { \ - (list1) = (list2); \ - } else { \ - type tmp; \ - for (tmp = (list1); tmp->next; tmp = tmp->next) ; \ - tmp->next = (list2); \ - if (list2) { \ - (list2)->prev = tmp; \ - } \ + DLIST_REMOVE(list, p); \ + DLIST_ADD(list, p); \ +} while (0) + +/* + demote an element to the end of a list. + Note that 'type' is ignored +*/ +#define DLIST_DEMOTE(list, p, type) \ +do { \ + DLIST_REMOVE(list, p); \ + DLIST_ADD_END(list, p, NULL); \ +} while (0) + +/* + concatenate two lists - putting all elements of the 2nd list at the + end of the first list. + Note that 'type' is ignored +*/ +#define DLIST_CONCATENATE(list1, list2, type) \ +do { \ + if (!(list1)) { \ + (list1) = (list2); \ + } else { \ + (list1)->prev->next = (list2); \ + if (list2) { \ + void *_tmplist = (void *)(list1)->prev; \ + (list1)->prev = (list2)->prev; \ + (list2)->prev = _tmplist; \ } \ + } \ } while (0) #endif /* _DLINKLIST_H */ |